Where Does the Smell of Rain Come From?

You’ve fired up the grill, set up the badminton net, are those dark clouds on the horizon? Don’t check your phone, your nose knows! Our noses can detect up to a trillion different scents, and many of them are deeply tied to our memories and our emotions. Like your grandma’s house, your first dog, or . . . the smell of rain. Storm winds carry an orchestra of separate smells, but the earthy odor that precedes a storm can be traced to three chemical sources. Before a thunderstorm, you’re probably smelling ozone, which interestingly gets its name from the Greek word meaning “to smell”. The electrical charge of lightning high up in approaching storm clouds splits oxygen gas into separate atoms, some of those can reform into ozone.

It’s swept ahead of the advancing storm by windy downdrafts, and down to your nose level. As rain begins to fall, a new smell springs from the soil: the pleasantly pungent perfume we call “petrichor”. Petrichor gets half its name from the ethereal essence that flowed through the veins of Greek gods and half from the stones of the Earth, which pretty much captures both its science, and the powerful feels I get when I smell it. When decomposed organic material is blown airborne from dry soil, it lands on dirt or rocks, where it’s joined by minerals and the whole mixture is cooked into a magical medley of molecules. Falling raindrops then send those chemicals airborne right into your nostalgic nostrils.

When there’s no rain around, those same chemicals remain in the soil, where they signal plants to halt their roots from growing or prevent seeds from sprouting when there’s no water to drink. Petrichor: it’s for the plant that’s tired of waiting . . . to germinate. Bacteria in the soil also contribute to petrichor by releasing a chemical called geosmin, that’s the same compound that gives beets their earthy flavor. There’s other purposes for petrichor besides showering us with emotion. It thought to attract camels to desert oases, who slurp up and transport the soil bacteria across the sands. Petrichor that’s washed into rivers and lakes also seems to signal fish that it’s time to spawn.

There’s nothing like a rainstorm to spark a little romance, I guess. So next time you smell a summer storm a-coming, take a minute to think about what that rock over there is trying to tell you. Stay curious. And smell ya later. Why are sharks so scary? Bloodthirsty beasts just waiting out there in the waves to feast on human flesh. if only we could get rid of these guys our vacations would be so much safer, nothing to worry about while we’re surfing and frolicking out there in the ocean. Except that’s not the case. Crimson Eleven Delight Petrichor Crimson Eleven Delight Petrichor Whoa!

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